Pawl coupling



Jan. 19, 1965 H. J. scHwr-:RDHFER ETAL 3,166,171

PAWL COUPLING Filed May '2, 1962 rm 3 TH .a (i

UnitedStates Patent n 33,3 1 screams. (ci. isz-sa) This inventionrelates to pawl couplings, and more particularly to a pawl coupling forselectively transrnitting torque between elements of a bicycle hub andthe like while the elements rotate relative to each other in onedirection, the elements being free to rotate relative to each other inthe opposite direction.

Pawl couplings rely on pawls mounted on a supporting carrier for pivotalmovement about pivot axes spacedly parallel to the axis of rotation ofthe pawl carrier relative to a ratchet which is engaged by the pawls. lna bicycle hub, the space that would be required for mounting the pawlson the carrier by means of journals and annular bearings is not readilyavailable, and it is usual to mount the pawls in pockets of the pawlcarrier which prevent axial movement of the pawls. lA spring retains thepawls in their pockets, and adequately secures them against undesiredradial movement in known pawl couplings.

Accidental circumferential movement of the pawls Vfrom their normalpositions is a source of malfunctioning in conventional couplngsof thistype. A pawl displaced from its pocket in a circumferential direction byvibration or by the normal operating stresses in the coupling is apt towedge between the pawl carrier Vand `the ratchet, and not only to makethe bicycle inoperative until the pawl is removed from wedgingengagement, but also to cause permanent damage to elements of thebicycle hub.

Pawl couplings have a particularly important function in multiple-speedbicycle hubs with or without coaster brakes, and the coupling of theinvention will be disclosed hereinafter in its application to amultiple-speed coaster hub. It will beV understood, though, that theinvention is not limited to the specic application chosen as an examplefor the purpose of the disclosure.

The object'ot` this invention is to provide a pawl coupling havingparticular utility in such multiple-speed hubs for bicycles and thelilce, and in Vfree-wheeling bicycle hubs in general, and free from theVshortcomings of known pawl couplings. v

lMore particularly, the'inven'tion aims at a pawl coupling in whichaccidental circumferential movement of. the pawls relative to the pawlcarrier is safely prevented.

Another object is the provision of a pawl coupling ti e Working elementsof which are of such a shape as to be inexpensively manufactured toprecise tolerances.

A further object is a pawl coupling in which wear of the workingelements Vis distributed in'such a manner as to provide long usefulservice of the coupling before replacement of pawls becomes necessary. j

An additional object is a pawl coupling which occupies but a minimum ofspace and therefore lends itself to application in the rear wheel hub ofa bicycle without crowding other hub elements. Y

With these and other objects in View, as will hereinafter more fullyappear, and will be more particularly pointed out in the appendedclaims, reference is now made to the following description taken inconnection with the accompanying drawing in which:

FIG. l shows a three-speed coaster hub for a bicycle airain; vPatentesJas. regress' lee Y 2- y equipped with two pawl couplings of theinvention, one half'of the hubbeing shown in axial section, the correspending axial section of the non-illustrated ,half being ,substantiallyamirror image of Vwhat is seen in FIG. l;

FlG. 2 shows the hub of FIG. 1 in Vradial section on the line .ll-Il;

FIG. 3 illustrates the device of FIG@ 2in a different operativeposition;

FIG. 4 shows a detail of FIG. 2 on an enlarged scale; and

FIG. 5 shows a detail of FIG. 3 on a larger scale. Referring initiallyto FIG. v 1, there is seen a coaster hub for a bicycle which will bedescribed hereinafter only to the extentnecessary for an understandingof this invention. All other elements. of the hub arermounted on a shaft2li which is normally lixedly mounted in the rear forli or" a bicycle intheA usual manner.. Two in ternal bearing race members 2l, 22 areVlixedly mounted on respective axial end portions of the shaft 2li. Aset of bearing balls 23 rotatable on the bearing member 21 supports oneaxialend of a tubular driver member 24 fixedly secured to adrive'sprocket 28. The sprocket which extends radially outward oftheremainder of the hub structure is engaged by a driving chain of thebicycle Vin the normal operating condition of the hub.

A hub shell 25 which envelops most of the movable elements oi the hub isof elongated tubular shape and has two flanges 5 to which wire spokesmay be attached.

A. tubular outer .bearingV race member. 45 is ixedly mounted in oneaxially terminal portion of the shell 25 and rotates onV bearing balls26 interposed between the outer bearing member 45 and the. driver member24. The other axially terminal portion of the hubV shell 25 constitutesan outer bearing race for a set of bearing balls 27 which roll Von themember 22. y

Planetary gearing in the hub shell 25 provides three Y transmissionratios between the sprocket 28 and the hub shell '25. rlfhe gearingconsists ofa sun wheel 32 -iixed on the shaft Ztl, a ring gear 33integral with a flange 7 and coaxial with the shaft, and three planetwheels 31 of which one only is visible in the drawing. The planet wheels3l simultaneously mesh with the sun wheel 32 and the ring gear 33. Theplanet wheels 31 are rotatable on a planet carrier 29 on respective pins3i?. The planet carrier 29 is rotatably mounted on the shaft 2t).

The planetary gearing is coupled to the driver Amember 24 by a `couplingsleeve 34 movably mounted on the shaft l 2li.- TheV sleeve is equippedlwith two external axially spaced toothed rims. A first rim 35 havingaxially elongatedteeth engages internal axially elongated teeth 36 ofthe driver member 24 to ensure joint rotation of the driver member 24and of the coupling sleeve 34 in any axial position of the latter. Asecond external toothed `rim 37 of the sleeve '34 is seen in FlG. l toengage a toothed ring 38 lixedly secured to lthe planet carrier 29 bythe pins 3l?.

The coupling sleeve 34 is axially movable on the shaft VZtl by means ofa speed changing mechanism which includes a linlc chain 39 connected tomanual controls on the bicycle in a well-known manner, Anot-furtherillustrated. The chain is attached to one end of a rod 40 which isaxially slidable in a central cavity of the shaft 20. The other end ofthe rod 49 is secured to a sliding' block llrllguided in a slot of theshaft 20 and radially projecting into a conforming recess of thecoupling sleeve 34. A helical return spring 42 interposed between thebearing member 21 and` the block 41 permanently "urges thev sleeve 34 tomove away from the driver member 24 intoY the position illustrated inFIG. 1 in which further movement of the sleeve 34 is prevented byabutment of the block 4l against a portion of the shaft 20. i- Y Yinternal toothed rim..43 on a tubular axial extension of ithe flange 7.A U-shaped vflat disc 44 is arranged movably astride the coupling sleeve34. When the sleeve 34 sassari iig entrained by the rim 37,v'axiallymoves the pawl carrier toward the outer bearing member 45 andinto engagement of the pawls' 9 with an annular conical face portion 12moves; from the position `illustrated'in FIG. 1y into a' positionofengagernent ofits toothed rim 37 with the internal rim 43 of the ange7, the rim 37 axiallyabuts against thedisc 44. y

An annular pawl carrier 6 is mounted on anrouterjcylindricalface of theaforo-mentioned extension of the flange 7. Conventional axiallyelongated ribs and recesses on opposite cylindricalrfaces of theextension and of the pawl carrier, not visible in the drawing, permitthe .carrier 6 to move axially on theY extension, but prevent relativerotation. The pawl carrier 6 is an'element of a pawl coupling accordingto this inventionwhich is'seen in more detail in the radially sectionalviews of FIGS. 2 to V5.

The outer cylindrical face of the pawl carrier 6 hasV two diametricallyopposite grooves 18 which extend over the of the bearing member, asbetter seen inl FGS. 2 to 5 Vwherein FIGS. 2 and 4 show radial viewscorresponding 1toFIG. l, and FIGS. 3 and 5 vshow the position ofthepawls 9 when engaged by the conical face portion 12. An

axial end portion of a ridge 19 on the radially outer face of the pawl 9abuts against the conical face portion12 of the bearing member 4S duringthe axial movement ofthe pawl carrier, and the' pawl is pivoted radiallyinward until it clears the ratchet 16 of the ring 11.

ln the relative position of thehub elements described in the precedingparagraph, motion is transmitted vfrom the sprocket ZB t-o the hub shellby way of the driver vmember 24, the'coupling sleeve 34, the ring gear33, the planet wheels 31, the planet carrier 29, the brake cone 1, the

entire axial length of the carrier and are axially open.

These grooves constitute pockets in each of which a pawl 9 is arranged.VThe pawls 9 cooperate with inclined al! ternating long and short Vfaceportions of an internal ratchet 10 on a rotatable ring 11 in aconventional manner.` Axially projecting claws on the ring 11 and `onthe outer bearingrace member 45 provide a coupling beftween the ring 11and the hub shell 25 which permits relative axial movement withoutdisengagement.

An integral hub portion of the planet carrier Z9 has an Y outercylindrical surface which carries at'threads 46 engaged with matingthreads on a brake cone 1. A conical outer face 47 of the brake cone 1is axially engageable with an inner conical face 4S on an axially`slotted brake sleeve 49 which is secured against rotation relative tothe shaft 29. Expansion of the. sleeve 49. by axial engagement withv thebrake cone 1 forces the sleeve 49 into o frictional braking engagementwith an inner surface of the hub shell 25. A second pawl couplingconnects the brake cone 1 to the hub shell Z5. In this coupling,.whichis substantially identical in structure and operation with theafore-described coupling, the brake cone 1 constitutes the pawl carrierand its outer cylindrical face carries two pawls 3 which are urged intoengagement with an internal As illustrated inFIG. the planetary gearingis set .o for its highestspeed. VDriving torque is transmitted from thesprocket 28 to the hub shell 215 by means of the .driver member 24, thecouplingsleeve 34, the planet Y carrier 29, the planet wheels, the ringgear, the

pawls 3 Vand the ratchet 4. The angular movement o f the hub shell 25during each revolution ofthe sprocket 28 is at its lowest value..

The pawl coupling of the invention will nowrbe described in more detailwith particular reference toFIG. 4.

The pawl carrier pockets 18 are axially open grooves of uniform radialsection andarci readily formed by breaching, die-slotting or othersimple operations. The depth of each pocket increases uniformly in acircumferential direction, but the deepestrportion yof the ypocket isfurther recessed to form an axially elongated trough 5'@ of cylindricalshape. v

rl`he pawls 9 each have an inner portion shaped to conform to thecontour of the corresponding pocket l?,Y The pawls are of elongatedcross section in a radial plane. One of the longitudinal end portions ofeach pawl carries an integral projection 16 which is matingly receivedVin the trough 5@ of the pocket 18 so that the trough and projectionjointly constitute a pivot for the pawl. The pawls are slotted in acommon radial plane. The slot 51 lof each pawl is open in a radiallyoutward direction and in both circumferential directions in alloperative posi.

tions of the pawl on the cartier 6. o A circumferential slot 52 in thecarriery 6 is aligned with the slots 51 of the pawls 9. A wire spring 3having the This edge portion is circumferentially spaced from .the

axis of the cylindrical projection 16 so that the pressure of the springS tends to pivot the outer portion of the pawl,

including the slotted tip ll7,`outward of theupocket 18,V

and into a position of engagement with the internal ratchet 10 ofthe'ring 11. /The tips 17 arefradially tapered as seen in FIGS. 2V to5,Y and axially tapered as is .seen in the projection 16 with theconforming cylindrical trough -pawls 9, the ring 11, and the outerbearngrace mem-' Y ber 45. Y l

vWhen the sleeve 34 is moved into engagement of its toothed rim v37 withthel internal toothed rim 43Y of the ring gear 33 withoutl displacingthe disc 44, the internal power train 4of thehub is constituted by .thedriver member 24, the coupling sleeve 34, the ring gear 33, the pawls 9,the ring 1-1, and the outer bearing race member 45 in thisorder. f

When the coupling sleeve 37 is moved further against the pressure of thespring 42, the toothedrims 37. and 43 remain engaged because of theaxial length Yof their'teetb,

member `24. The movement of the disc 44 as it is being The faceof thepawl 9 opposite the ratchet 10 has an` axially `elongated projectingridge 19. When' the ring 11 rotates faster thanfthe pawl carrier 6,sliding contact` beratchet, and from the concomitant wear.

When the pawl carrier 6 is shifted toward the sprocket 2S by the speedchange mechanismactingV on theV disc 44 against the return springs 42`and 53, axial end portions of the ridges V19 engage a conically`tapering abutment face 12 on the Vbearing member 45, and the pawls 9 arethereby retracted into their pockets 18 against the force of the spring8 as seen in FIG.Y 5. The pawl carrier 6 with itsv pawls 9 may nowaxially enter a central bore 13 in the bearing member 45. The diameterof this bore is smaller meant posed between the brake cone 1 and the hubshell 25 are v analogous to` those of the coupling illustrated in FIGS.2 to 5. More specifically, the brake conel lis formed withperipheralzpockets 54 which extend lover the entire axial length of thecone and in-tersect the conical face 47. The

pawls 3 are pivoted Yon the brake cone 1 in respective pockets 54 bymeans of cylindrical projections and corresponding troughs in the brakecone 1. No provisions need be made for retraction of theV pawls 3 intothe corresponding pockets 54.

gage thefcooperating ratchet.vv The protection provided for the pawltips against wear by the ridges 19 the dimensions of which are far lesscritical, thus materially extends the useful life ofthe coupling beforereplacement of pawls becomes-necessary. The relatively broad ridges s Y19 also are better suited than the tips 17 .to take the The ratchet 4 onthe hub Vshell 25 has teeth of sufficient axial lengthto engage thepawls 4 during the axial movement of the brake cone 1 on the threads 46.Such movement is induced in a known manner by a spring 5S which issecured against axial movement in an annular groove of the brake cone 1.The spring is of approximately circular shape, rotatable in the grooveabout the axis of the shaft 20, and tensioned` to frictionally engagethe cone 1 during relative rotation. A free end portion of the spring 55extends radially outward into an axial slot of the brake sleeve 49 sothat the friction of the spring 55 impedes rotation of the brake cone 1relative to the brake sleeve 49, and to the shaft on which the sleeve 49is secured against rotation.

The pawls 3, 9 may be identical in shape and dimensions, and arepreferably manufacturedl from rods having the cross section evident fromFIGS. 2 to 5. Pawls are made from such rods by transverse cutting. Thecuts are.

of alternating depth so that a first cut will produce a slot S1, and thenext cut will sever the slotted pawl 3, 9 from the remainder of the rod.When the pawls 9 are inserted in the carrier 6, the pressure of thespring 8 positions them in such a manner that the straight bottoms ofthe slots 51 extend along chords of the circle formed by the spring 8,and the tips 17 project radially beyond the cylinder 14. During assemblyof the pawl carrier With the other elements of the hub, the Pawls may bepushed back into their retracted position. When in place within the hubshell 25, they are urged by the pressure of the spring S into resilientengagement of their ridges 19 with the ratchet 10.

The pawl coupling of the invention is readily manufactured by relativelysimple and inexpensive methods. It occupies very little space in the hubshell 2S. The pawls 3, 9 do not require journals cooperating withannular bearings which complicate assembly and occupy valuable space.Yet, the pawls are secured relative'to the supporting carrier against`circumferential displacement, and are pivotable about respective fixedaxes. Malfunctioning of the hub by circumferential displacement of thepawls, and wedging of the same between the pawl carrier and thecooperating ratchet member is safely avoided. Neither vibration nor thestresses inherent in power transmission can aifect the positions of thepawls. The invention Vdoes not rely on walls of the pawl receivingpockets in the pawl carriers for axially securing the pawls, and thepockets may therefore be formed without axial walls, thereby greatlyfacilitating manufacture of .the pawl carriers.

ln the preferred embodiment of the pawl carrier illustrated in thedrawing, the cylindrical projection 16 extends over only a portion ofthe radially inward face of each pawl 3, 9, and such a relatively smallcylindrical projection is sufficient to provide the desired pivotal wear`inherent in the retracting of the pawls 9 by axial contact with theconical face 12 of the bearing member 45. Y

It should be understood of course that the foregoing disclosure relatesto only a preferred embodiment of the invention, and that it is intendedto cover all-changes and modifications of the example of the inventionherein chosen for `the purpose of jthedisolosure whichdo notV constitutedepartures from the spirit andscopel of 4the invention set forthin theVappended claims.

What we claim is: 1. A pawl coupling for a bicycle hub and prising, incombination; j

(a) a circular ratchet; (b) a pawl carrier rotatable relative to saidratchet in two directions in a radial plane about a common axis, saidpawl carrier having a circumferential face portion opposite saidratchet, said face portion defining ,a radially open recess therein, atleast a portion of said recess being cylindrical transverse of saidplane; (c) a pawl having an inner portion received in said recess andsubstantially `conforming to said cylindrical portion thereof forpivoting movement about i said pivot axis, and an outer portionengageable with said ratchet, said outer portion including (l) firstabutment means circumferentially engageable with said ratchet when saidpawl carrier rotates in one of said directions for transmitting torquebetween said pawl carrier and said ratchet, and (2) second abutmentmeans radially engageable with said ratchet for sliding movement of saidsecond abutment means relative to said ratchet, and for substantiallypreventing Contact between said first abutment means and said ratchetwhen said pawl carrier rotates in the other direction; and (d) resilientmeans for urging said inner portion into conforming engagement with saidcylindrical recess portion. Y 2. A pawl coupling as set forth in claiml, wherein the recess defined by said face' portion is of substantiallyuniform cross section transversely of said common axis, and extends in adirection parallel to said common'axis; said pawl carrier is formed witha circumferentially elongated the like4 corngroove; and said resilientmeans includes elongated springv means retained insaid groove andengaging said pawl-I ing said pawl about said pivot axis into engagementofY said outer portion thereof with said ratchet,V said outer portionhaving a tip part constituting said rst abutment means, and a ridge partcircumferentially spaced vfrom said tip part and constituting saidsecond abutment means.

4. A pawl coupling as set forth in claim 1, further comprising thirdabutment means having a conically flaring annular abutment face aboutsaid common axis; and

means for moving said pawl carrier and said third abut-iV ment meansrelative to each other in the direction of said common axis for axiallyabutting engagement of said abutment face with said pawl, said resilientmeans including spring means yieldably exerting pressure on said pawlfor pivoting the same about said pivot axis into engagement of saidouter portion thereof with said ratchet,

about a pivot axis `said outer portion having a i 7 Y Y Y tip partconstituting said first abutment means,'and a ridge part axiallyprojecting to- Vward said abutment face beyondsaid tipkpart forengagevlrnent therewith vduringsaid Vrelative, movement ofV said Y.

pawli carrier and said abutment means'in'the direction' of said commonaxis for pivoting said pawl against the 'pressure vof said spring meansVout of engagement with said ratchet.

about said pivotf axis into abutting engagement of said outer portionthereof with said ratchet, said outer por*- tion having a tip part'constituting said first abutment.

means and being circumferentially Vabuttable against said j shorterratchet fa'ces when saidpawl carrier rotates in Y said one direction,and a ridge part constituting said sec- -ond abutment means,v said ridge-part beingA circumferen- 1 tidly spacedrfromtsraidjtip part.. and being"radially abuttable against the` longer ratchet faces for sliding move-kment of saidridge vpart relativcito the latter ratchet faces when saidpawl carrier rotates "in said otherrdirection, said tip part'beingspaced fromeach longer ratchet face while said ridge part radially abutsagainstthe same. I Refereucesited by the Examiner UNITED` STATES PATENTS7j/59V Schwerdhofer. y i 2,988,186 V6/61 ,potter T 19'2-64V FOREIGNPATENTS 997,737 9/51 (France. 824,448 12/51 Germany.

DAViD J. WILLIAMOWSKY, Primary Examiner.

1. A PAWL COUPLING FOR A BICYCLE HUB AND THE LIKE COMPRISING, INCOMBINATION: (A) A CIRCULAR RATCHET; (B) A PAWL CARRIER ROTATABLERELATIVE TO SAID RATCHET IN TWO DIRECTIONS IN A RADIAL PLANE ABOUT ACOMMON AXIS, SAID PAWL CARRIER HAVING A CIRCUMFERENTIAL FACE PORTIONOPPOSITE SAID RACTHET, SAID FACE PORTION DEFINING A RADIALLY OPEN RECESSTHEREIN, AT LEAST A PORTION OF SAID RECESS BEING CYLINDRICAL ABOUT APIVOT AXIS TRANSVERSE OF SAID PLANE; (C) A PAWL HAVING AN INNER PORTIONRECEIVED IN SAID RECESS AND SUBSTANTIALLY CONFORMING TO SAID CYLINDRICALPORTION THEREOF FOR PIVOTING MOVEMENT ABOUT SAID PIVOT AXIS, AND ANOUTER PORTION ENGAGEABLE WITH SAID RATCHET, SAID OUTER PORTION INCLUDING(I) FIRST ABUTMENT MEANS CIRCUMFERENTIALLY ENGAGEABLE WITH SAID RATCHETWHEN SAID PAWL CARRIER ROTATES IN ONE OF SAID DIRECTIONS FORTRANSMITTING TORQUE BETWEEN SAID PAWL CARRIER AND SAID RATCHET, AND (2)SECOND ABUTMENT MEANS RADIALLY ENGAGEABLE WITH SAID RATCHET FOR SLIDINGMOVEMENT OF SAID SECOND ABUTMENT MEANS RELATIVE TO SAID RATCHET, AND FORSUBSTANTIALLY PREVENTING CONTACT BETWEEN SAID FIRST ABUTMENT MEANS ANDSAID RATCHET WHEN SAID PAWL CARRIER ROTATES IN THE OTHER DIRECTION; AND(D) RESILIENT MEANS FOR URGING SAID INNER PORTION INTO CONFRONTINGENGAGEABLE WITH SAID CYLINDRICAL RECESS PORTION.